Anonymous Methods and Code Analysis

Note

This article applies to Visual Studio 2015. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here

An anonymous method is a method that has no name. Anonymous methods are most frequently used to pass a code block as a delegate parameter.

This topic explains how Code Analysis handles warnings and metrics that are associated with anonymous methods.

Anonymous Methods Declared In a Member

Warnings and metrics for an anonymous method that is declared in a member, such as a method or accessor, are associated with the member that declares the method. They are not associated with the member that calls the method.

For example, in the following class, any warnings that are found in the declaration of anonymousMethod should be raised against Method1 and not Method2.

      Delegate Function ADelegate(ByVal value As Integer) As Boolean
Class AClass

    Sub Method1()
        Dim anonymousMethod As ADelegate = Function(ByVal value As Integer) value > 5
        Method2(anonymousMethod)
    End SubSub Method2(ByVal anonymousMethod As ADelegate)
        anonymousMethod(10)
    End SubEnd Class

      delegate void Delegate();
class Class
{
    void Method1()
    {
        Delegate anonymousMethod = delegate()
        {
          Console.WriteLine("");
        }
        Method2(anonymousMethod);
    }

    void Method2(Delegate anonymousMethod)
    {
        anonymousMethod();
    }
}

Inline Anonymous Methods

Warnings and metrics for an anonymous method that is declared as an inline assignment to a field are associated with the constructor. If the field is declared as static (Shared in Visual Basic), the warnings and metrics are associated with the class constructor; otherwise, they are associated with the instance constructor.

For example, in the following class, any warnings that are found in the declaration of anonymousMethod1 will be raised against the implicitly generated default constructor of Class. Whereas, those found in anonymousMethod2 will be applied against the implicitly generated class constructor.

  Delegate Function ADelegate(ByVal value As Integer) As BooleanClass AClass
Dim anonymousMethod1 As ADelegate = Function(ByVal value As    Integer) value > 5
Shared anonymousMethod2 As ADelegate = Function(ByVal value As     Integer) value > 5

Sub Method1()
    anonymousMethod1(10)
    anonymousMethod2(10)
End SubEnd Class

      delegate void Delegate();
class Class
{
    Delegate anonymousMethod1 = delegate()
    {
       Console.WriteLine("");
    }

    static Delegate anonymousMethod2 = delegate()
    {
       Console.WriteLine("");
    }

    void Method()
    {
       anonymousMethod1();
       anonymousMethod2();
    }
}

A class could contain an inline anonymous method that assigns a value to a field that has multiple constructors. In this case, warnings and metrics are associated with all the constructors unless that constructor chains to another constructor in the same class.

For example, in the following class, any warnings that are found in the declaration of anonymousMethod should be raised against Class(int) and Class(string) but not against Class().

  Delegate Function ADelegate(ByVal value As Integer) As BooleanClass AClass

Dim anonymousMethod As ADelegate = Function(ByVal value As Integer)
value > 5

SubNew()
    New(CStr(Nothing))
End SubSub New(ByVal a As Integer)
End SubSub New(ByVal a As String)
End SubEnd Class

      delegate void Delegate();
class Class
{
    Delegate anonymousMethod = delegate()
    {
       Console.WriteLine("");
    }

    Class() : this((string)null)
    {
    }

    Class(int a)
    {
    }

    Class(string a)
    {
    }
}

Although this might seem unexpected, this occurs because the compiler outputs a unique method for every constructor that does not chain to another constructor. Because of this behavior, any violation that occurs in anonymousMethod must be suppressed separately. This also means that if a new constructor is introduced, warnings that were previously suppressed against Class(int) and Class(string) must also be suppressed against the new constructor.

You can work around this issue in one of two ways. You could declare anonymousMethod in a common constructor that all constructors chain. Or you could declare it in an initialization method that is called by all constructors.

See Also

Analyzing Managed Code Quality